NSW coastal regions have been hit by torrential rainfall, flooding similar to levels three decades ago and power outages as a severe weather system has moved northward.

The NSW State Emergency Service says it has received 1600 calls for help since Friday, including 800 overnight and involving 37 flood rescues. About 700 of the calls were on the South Coast and 550 in Greater Sydney.

Flooding similar to an event in June 1991 occurred along the Shoalhaven River at Nowra and Terara, the SES says. Levels are falling again this afternoon.

Bureau of Meteorology figures show rain totals over the South Coast and Illawarra in the past few days include falls of 373mm at Nowra.

A severe weather warning is in place today for a region extending from Ulladulla to Port Macquarie.

“A trough along the NSW coast, together with multiple low centres within the trough, [is] bringing increased winds and surf,” the bureau says.

The Insurance Council of Australia says insurers have received only a small number of claims and are standing by to assist customers.